The invention relates to a method of operating a supercharged internal combustion engine, in particular an auto-ignition internal combustion engine with direct fuel injection including a cylinder with a cylinder head having inlet and outlet valves and a piston movably disposed in the cylinder.
In direct-injection internal combustion engines with auto- or compression-ignition, lean homogeneous fuel/air mixtures are often made to auto-ignite so that high engine efficiency levels and lower exhaust emissions are obtained. In such internal combustion engines, that is, internal combustion engines with compression ignition, a lean basic mixture of air, fuel and retained exhaust gas is generally formed during operation of the engine under partial load and auto-ignited. During full load engine operation, a stoichiometric mixture is frequently formed and spark-ignited. In order to optimize the operation of such internal combustion engines, attempts are made to extend the compression ignition combustion operating mode and the characteristic diagram range in the compression ignition mode of operation toward larger loads. Such extension of the operating range with compression ignition however is restricted by a lack of air since sufficient quantities of fresh air for the conversion of large quantities of injected fuel with a predefined overall level of efficiency are not availably, in particular in the full load range and at high rotational speeds of the engine. One possible way of overcoming such a lack of air resides in supercharging the engine with fresh air.
According to the current state of the art, it is difficult to control supercharged internal combustion engines with compression ignition since the time of auto-ignition depends very greatly on the parameters of the engine and the ambient conditions.
It is therefore the object of the invention to provide a method of operating a supercharged internal combustion engine under optimized conditions in terms of efficiency both in an auto-ignition mode and in a spark ignition mode of operation.